In the processing of substrates, such as semiconductor wafers and displays, a substrate is placed in a process chamber and exposed to an energized gas to deposit or etch material on the substrate. During such processing, process residues are generated and deposited on internal surfaces in the chamber. For example, in sputter deposition processes, material sputtered from a target for deposition on a substrate also deposits on other component surfaces in the chamber, such as on deposition rings, cover rings, shadow rings, inner shield, upper shield, wall liners, and focus rings. In subsequent process cycles, the deposited process residues can “flake off” of the chamber component surfaces to fall upon and contaminate the substrate. Consequently, the deposited process residues are periodically cleaned from the chamber surfaces.
However, it is difficult to clean process deposits that contain metals from chamber components, such as for example tantalum and tantalum nitride metals, especially when the components themselves are made of metal-containing materials.
For example, when tantalum is sputter deposited onto the substrate, some of the sputtered tantalum deposits upon the adjacent chamber component surfaces. These tantalum deposits are difficult to remove because cleaning solutions suitable for their removal are also frequently reactive with other metals, such as titanium, aluminum, copper and stainless steel, which are used to form chamber components. Cleaning of tantalum-containing materials from such surfaces can erode the components and require their frequent replacement. The erosion of metal surfaces can be especially problematic when cleaning textured metal surfaces. These surfaces can have crevices and pores in which tantalum-containing process residues get lodged, making it difficult to remove these residues with conventional cleaning processes.
When conventional cleaning methods are used to clean metals such as tantalum, a relatively large amount of the metal-containing material generated in these processes is typically not recoverable. For example, it is estimated that in many tantalum deposition processes, only about one-half of the sputtered tantalum material is deposited on the substrate, the rest being deposited on component surfaces within the chamber. Conventional cleaning methods frequently dispose of the used cleaning solutions along with the dissolved tantalum material. Thus, a large amount of tantalum material is wasted after it is cleaned off the chamber surfaces, resulting in an estimated loss of about 10,000 to about 30,000 pounds of tantalum per year. The disposal of metals such as tantalum is environmentally undesirable and costly because high purity tantalum is expensive and fresh cleaning solution also has to be acquired.
Thus, it is desirable to have a method of cleaning metal-containing deposits such as tantalum-containing deposits from surfaces of components without excessively eroding the surfaces. It is also desirable to reduce the waste of the tantalum materials cleaned off the chamber surfaces, for example by recovering the tantalum materials.